A tubing hanger is installed in a well in order to achieve a conduit between a producing reservoir of oil or gas and the surface and to provide well control and protection to the localised environment. The tubing hanger is used to support tubulars that also aid in retrieving these hydrocarbons. Typically these tubulars can range from 2-⅜ inch outside diameter to 9-⅝ inch outside diameter. A typical tubing hanger is about 18-¾ inch in outside diameter at the top and 9-⅝ inch at the bottom, and is designed to fit to a subsea tree of the well where it is pressure tested.
In the majority of subsea wells, the quality of the produced fluids and the addition of components such as subsurface safety valves and bottom hole pressure gauges require that small capillary tubing be installed in the well. The capillary tubing can be in-the form of a control line used to transport chemicals to chemical injection valves or to provide hydraulic fluids to mechanical devices. The capillary tubing can also be in the form of I-wire (have I-wire installed internally) used to transport electrical signals to and from downhole devices such as pressure gauges.
In a typical offshore installation, the capillary tubing is clamped to the tubing as it is run into the well, and then terminated at the tubing hanger. The connection of the capillary tubing to the hanger is time consuming and difficult, bearing in mind that this operation is often performed on a floating offshore rig, and sometimes in severe weather conditions. Typically the control line is connected to the hanger between a shroud and a tubing in the form of a pup joint through which the hydrocarbons flow. The capillary tubing must fit between the shroud and pup joint and be connected and tested pressure tight. The time to make up these connections can be considerable, therefore adding significantly to the cost of installing the capillary tubing in a well.